1. Field of the Invention
The present invention relates to vehicular adaptive cruise control apparatus and method for an automotive vehicle having a traveling control function of following a preceding vehicle which is a controlled system of a following control of the vehicle (hereinafter, also referred to as a host vehicle) and is traveling on the same traffic lane in a forward direction of the host vehicle.
2. Description of the Related Art
A Japanese Patent Application First Publication No. 2000-43611 published on Feb. 15, 2000 exemplifies a previously proposed adaptive cruise control apparatus. In the above-identified Japanese Patent Application First Publication, the previously proposed adaptive cruise control apparatus enlarges a magnitude of an acceleration from an actual host vehicular velocity to a target vehicular velocity so as to vary the actual host vehicular velocity quickly and smoothly to the target vehicular velocity when a vehicular run state is transferred from a cruise run state at a low velocity to the same cruise state at a high velocity. On the other hand, when the target vehicular velocity is varied under the cruise run state at the high vehicular velocity, the magnitude of the acceleration is made small so as to facilitate a fine setting of the host vehicular velocity.
The previously proposed adaptive cruise control apparatus, however, determines a target acceleration in accordance with the host vehicular velocity at a time point at which the acceleration is started. Hence, for example, suppose that, in a case where the host vehicle is following the preceding vehicle at a lower vehicular velocity than a driver""s set vehicular velocity (so-called, a set vehicle speed), the preceding vehicle has changed its traveling traffic lane from the same traffic lane as the host vehicle to the adjacent traffic lane or the host vehicle has changed its traveling traffic lane to the adjacent traffic lane. At this time, the preceding vehicle becomes unrecognized and the host vehicle is accelerated to reach to the set vehicle speed. However, when the vehicular velocity of the host vehicle at the time of an acceleration start is low, a magnitude of the acceleration is set to be large.
Although a quick change in the actual vehicular velocity can occur, a large acceleration state is maintained even if the vehicular velocity approaches to a high vehicle velocity region. As a result of this, the large acceleration cannot accommodate the vehicular run control itself to a traveling feeling of the vehicular driver and such a vehicular run as described above gives an unpleasant feeling to the vehicle driver.
On the other hand, suppose that such an acceleration that the unpleasant feeling is not given to the vehicle driver is set and the vehicular acceleration is carried out at the set acceleration in spite of the vehicular velocity at the time of acceleration start. The vehicle driver does not feel unpleasant since the acceleration is constant. However, an arrival time duration for the host vehicle to arrive at the set vehicle speed is varied depending upon the vehicular velocity at the time of acceleration start. Hence, when the vehicular velocity at the time of acceleration start is low, the arrival time duration to the set vehicle speed becomes long. Consequently, the vehicle driver feels that a response characteristic of the adaptive cruise control becomes worsened.
It is, hence, an object of the present invention to provide vehicular adaptive cruise control apparatus and method for an automotive vehicle which can obtain an acceleration performance with a high responsive characteristic without giving an unpleasant feeling to the vehicle driver.
According to one aspect of the present invention, there is provided an adaptive cruise control apparatus for an automotive vehicle, comprising: a vehicular velocity detecting section that detects a velocity of the vehicle; an inter-vehicle distance detecting section that detects an inter-vehicle distance between the vehicle and another vehicle which is traveling on the same traffic lane as the vehicle in a forward direction thereof; a driving force controlling section that controls a driving force for the vehicle to maintain the inter-vehicle distance at a target inter-vehicle distance to achieve the following run control when the inter-vehicle distance detecting section detects the inter-vehicle distance between the vehicle and the other vehicle and to maintain the velocity of the vehicle at a set vehicle speed when the inter-vehicle distance detecting section detects no other vehicle on the same traffic lane in the forward direction thereof; and an acceleration controlling section that sets an acceleration value at an initial stage of an acceleration in such a manner as to be larger than that at a later stage of the acceleration when the inter-vehicle distance detecting section transfers its other vehicle detection state from the detection state of the other vehicle to a non-detection state thereof.
According to another aspect of the present invention, there is provided an adaptive cruise control method for an automotive vehicle, comprising: detecting a velocity of the vehicle; detecting an inter-vehicle distance between the vehicle and another vehicle which is traveling on the same traffic lane as the vehicle in a forward direction thereof; controlling a driving force for the vehicle to maintain the inter-vehicle distance at a target inter-vehicle distance to achieve the following run control when the inter-vehicle distance between the vehicle and the other vehicle is detected and to maintain the velocity of the vehicle at a set vehicle speed when no other vehicle is detected on the same traffic lane in the forward direction thereof; and setting an acceleration value at an initial stage of an acceleration in such a manner as to be larger than that at a later stage of the acceleration when the other vehicle detection state is transferred from the detection state of the other vehicle to a non-detection state thereof.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.